Hybrid fuzzy logic control strategies for hot water district heating systems

Abstract

Hybrid fuzzy logic control (FLC) strategies for hot water district heating (HWDH) systems are designed. A non-linear dynamic model of a HWDH system (heated floor area 90 000 m2) with 21 dynamic equations is developed. The dynamic model consists of a boiler, pipe network, heaters and buildings. Six different hybrid control strategies involving FL and PI control were designed to regulate fuel firing rate, water flow rate or water temperature in the system. Simulation results show that the control strategies, based on the use of return water temperature and indoor air temperature predictor (IATP), give good zone temperature control. Pumping costs were reduced by modulating water flow rate in the system. Results also showed that the proposed hybrid control strategies could save up to 17% energy in buildings.